Depends on the car you ordered. If it's something they can move easier than the one you're trying to buy, they'd be more willing to make the swap. But if the car you ordered is really custom with not so popular combos, you're outa luck. Helps if the second car you're considering is from same dealer.
Doubt you can get same lease payment. Yes, it's technically a year older, but it's still brand new, and the options available on 2012 and 2013 are exactly the same.